Magneto



Nov. 22,1938. K, HARMON I 2,137,875

MAGNETO Filed Oct. 22, 1957 s Sheets-Sheet 1 mvamon' Emu-m A. (ZR/w A ORNEY Nam 1938. K. A. HARMON 5 MAGNETO I Filed 001;. 22, 1957 3 Sheets-Sheet 2 llllllll INVENTOR Patented Nov. 22, 1938 PATENT OFFICE MAGNETO Kenneth A. Harmon, Longmeadow,

Masa, assignor to Wico Electric Company, West Springfield,

Mass... a corporation of Massachusetts Application October 22, 1937, Serial No. 170,403

2 Claims.

This invention relates to improvements in high tension magnetos, such as are suitable for use as an ignition means for multi-cylinder internal combustion engines.

The general object of the invention is to provide in a high tension magneto an improved arrangement of parts, characterized by compactness and enabling the magneto to be made small in size and at the same time powerful and efficient.

The invention, for example, enables the magneto to be of such small dimensions that it may be mounted on and driven from the internal combustion engine in the same manner as the timerdistributer units now employed with the battery is ignition systems of automobiles.

Another object of the invention is to provide a high tension magneto, in which the stator is composed of a plurality of coils and cores mounted in a circular series around the magneto drive shaft go with the axes of coils, cores and shaft in substantiaily parallel relation, and in which the rotor, driven by the shaft, is composed of at least one and preferably two multi-polar magnets of high coercive force and very small size, one magnet-be- 25 ing located above and cooperating with the upper ends of the cores and the other being located be;- low and cooperating with the lower ends of the cores.

A further object of the invention is to provide a so high tension magneto which is designed for manufacture in quantities at low unit cost.

Other objects will appear as the detailed description proceeds and will be pointed out in the appended claims.

The invention will be disclosed with reference to the accompanying drawings, in which:

Fig. l is a full size, sectional elevational view of a magneto embodying the invention;

Figs. 2, 3 and 4 are cross sectional views taken 40 on the lines 2--2, 3- 3, and 4-4, respectively, of

Fig. 1;

Fig. 5 is a cross sectional view taken on the line 5-5 of Fig; 1, showing the timer mechanism;

Fig. 6 is a fragmentary sectional view taken on 45 the line 6-6 of Fig. 2;

Fig. '1 is a fragmentary exterior elevational view with parts broken away to show the mounting of the cores;

Fig. 8 is a fragmentary sectional elevatlohal 50 view taken on the line 8-8 of Fig. 2; and

Fig. 9 is a wiring diagram showing theelectrical connections.

Referring to these drawings: the magneto has been illustrated as of the so-called timer type,

55 having on the bottom part of its casing (Fig. 1)

a sleeve l0 adapted to fit in a socket of an internal combustion engine in the same manner as the usual timer-distributer unit used in battery ignition systems. The driving shaft H has a bearing in this sleeve and extends below it carrying an element 02 for coupling engagement with a shaft of the engine. The magneto casing has a seat 13 which is adapted to rest on and be supported by the end face of said socket. The sleeve I0 is held in such socket by suitable means (not shown), 10 engaging in the circumferential groove it of sleeve ill.

The magneto casing is constructed in three generally cylindrical sections l5, l6 and ll,

mounted one upon the other in superposed and 15 also in coaxial relation. Usually the upper section l'i carries a distributer cap l8, made of insulating material and mounted on, section ll for convenient removal in any of the usual and well known ways. The sections l5 and I! which may be made or iron or other metal or any other suitable material, have annular flanges such as l9 to fit into and engage the cylindrical outer wall of. the intervening section it, whereby the several sections are centralized one with another. These three sections are firmly held together by a series of cap screws ill (Fig. 6), which pass through sec tions 15 and it and thread into section II.

The middle section it is advantageously made of bakelite or similar material, molded in the form shown. It has a lower end wall 2| and, upstanding centrally therefrom, a sleeve 22 in the upper end of which is inserted a bearing 23 for shaft H. The upper end of sleeve 22 and the upper end of the outer cylindrical wall of casing 5 section It are formed with seats, upon which rests a top closure plate 24 of annular form,-such plate being preferably also made of bakelite. The parts l6, 2!, 22 and 24 form a closed'annuiar chamber in which all the coils of the magneto 40 are housed. The cores for these coils, as well as other non-coil-carrying cores pass through this chamber and have their ends projecting slightly above the top wall 24 and slightly below the bottom wall 2|.

Referring to Fig. 4, ranged in a circular series. rality, eight in this case, of

the cores and coils are ar- There are a plucores 25 spaced at equal angular intervals around shaft H and at equal radial distances therefrom. Alternate cores of the series carry coil units,-each such unit comprising a primary coil 26 and a secondary coil 21. As will be seenfrom Fig. 1, the axes of these cores and coils parallel the axis of shaft II. The cores may be fixed in their housing in any suitable way.

One desirable way is to make that portion of each core, which lies between the end walls 2| and 24; slightly wider than the portions of the core that pass through said walls. For example, the two outer laminations of each core may be made shorter as shown in Figs. 6 and 7, whereby shoulders 28 are formed. The walls 2| and 24 are formed with holes to fit the ends of the cores and the shoulders abut the inner faces of the two end walls. Then, when the cap screws 20 are tightened, the flange B9 of section ll will press the top wall 24 against the upper shoulder 28 of each core 25 and force these cores downwardly until the lower shoulder 28 of each engages the bottom wall 24.

Also located within the casing section I6 is a high tension conductor in the form of a circular band of metal 29 (Fig. 1) which is slipped into thecoil housing from its upper end and pressed downwardly until it seats on a shoulder formed on the inner wall of section l5. This band has struck out therefrom at suitably spaced intervals, spring fingers 30 adapted to engage,

' one with each, the high tension terminals 3! fixedto shaft ll.

coils 26 and 21 are slipped over the proper cores;

the necessary electrical connections are made; then the space within the coil housing is filled with waxor other suitable material; and the cover 24 is applied. This complete unit is then slipped over the shaft, which has been previously mounted in section I5 and onto its seat on the latter. The cap screws 20 are then applied to clamp the casing sections together.

The rotors are permanent magnets suitably The latter has a shoulder 36 to engage a seat formed on the inner face of the bottom wall of section l5. This shoulder 20 and a collar 31, fixed to shaft ll Just below the lower end of sleeve lli, hold the shaft in position axially. .The magnets are made of special steel of such-a class that very high coercive force can be obtained from magnets of very small dimensions. The magnetic rotors, as herein shown, are formed by casting. Each has as many arms 38 as there are cores, alternate arms being of opposite polarity (Figs. 2 and 3). The arrangement provides the equivalent of a circular series of horseshoe magnets (four in case) having the inner ends interconnected. The neutral points of each magnet lie nearest to the shaft l I and the arms of the magnets point outwardly, terminating with integral pole shoes 25 .for cooperation with the ends of cores 25. The upper magnet marked 11:. is mounted with its pole shoes 39 downturned toward and into close proximity with the upper ends of cores 25. The lower magnet marked m is mounted with its pole shoes 39 upturned toward and into close proximity with the lower ends of cores 2!. The arms ll of the lower magnet m lie directly beneath the arms of the upper magnet m but the arrange-.

ment is such, as will be clear from a comparison of Figs. 2 and 3, that beneath each pole shoe of magnet m is a pole shoe of oppositepolarity on the magnet m.

The magnets, as herein "shown, each have a central hole therethrough through which a noncircular section of shaft H loosely puss. Matrix metal 40 is cast in each such hole and arolmd the non-circular part of the shaft to hold each magnet thereto. This particular holding means 2 41, having a central opening in which the hollow hub 42 of a timer plate I! is mounted on ball bearings 44. This mounting enables the timer plate to be shifted angularly relative to shaft I! for spark timing purposes by any suitable means (not herein shown), in a manner well understood in the art. It willbe understood that plate 42 is normally stationary but capable of being angularly shifted for varying the timing of the spark. The upper end of shaft ll extends loosely through the hollow hub 42 and has fixed thereto a cam 45 for actuating the breaker point mechanism, opening and closing them in proper timed relation with the breaks in the magnetic circuit eifected by movement of the magnetic rotors m and m. Any suitable breaker point mechanism may be used for the purpose.

An exemplary form of breaker point mechanism is shown in Fig. 5. It includes relatively fixed and movable breaker points I and 41, the former being stationarily but adjustably mounted on timer plate 42 and grounded thereto and the latter being fixed to one end of a lever ll of insulating material pivotally mounted on a stud l9 and having its other end located so as to be engaged by cam 45. A spring II serves to move the lever 48 into engagement with the camand also as an electrical conductor to connect breaker point 41 to a terminal 6|, fixed to an insulating block 52 secured to plate 43. A condenser 64 is 7 also mounted on this plate and has one terminal grounded thereto, the other terminal being connected by a metal piece I! to terminal II.

- 56, mounted in cap II and having sockets I to receive the usual spark plug wires (not shown), and a brush 58, fixed to the upper end of shaft I I. The inner end of brush 5| is connected to a terminal 58 in cap lI,'-such terminal having a socket 62 to receive one end ofa high tension wire, the other end of which is received in socket I2 and connected to terminal 22 and thus to the high tension terminals .of all the secondary coils.

The electrical connections are shown in Pig. 9. The several primary coils 2! are connected in series and one terminal of one end coil of the series is grounded. The other end coil of the series is connected by a wire I to the terminal II and thus to the movable breaker point 41 and the insulated terminal of the condenser II. The primary coils are thus connected in a series circuit which can be opened and closed by the disengagement and engagement, respectively, of the breaker points 46 and 41. The secondary coils as shown, are connected in parallel, one terminal of each being grounded and the other termine] of each being connected, as described, to the terminal 22 in socket 22. The parallel connection of the secondary coils is nothowever,

essential. The various wire connections between nected to terminal 59 of the distributer by a wire 82.

The operation of the magneto will next be described. Assuming that the magnets m and 111. have been moved backwardly (clockwise) until they are positioned so that their pole shoes 39 overlie and underlie, respectively, the ends of cores 25, four magnetic circuits are then established,--one through each set of generating coils. For example, flux from each north pole of magnet m will flow down through a non-coil-carrying coreji to a south pole of magnet m and thence from an adjacent north pole of magnet m upwardly through a coil-carrying core 25 to a south pole. of magnet m. As the rotors turn in a counterclockwise direction, they will eventually assume the positions illustrated in Figs. 2 and 3 in which the magnetic circuits just described, will be broken at four points by air gaps 63 and other magnetic circuits will be established in an opposite direction through each set of generating coils. Thus, flux from each north pole of magnet m will now pass downwardly through a coil carrying core 25 to a south pole of magnet m and from an adjacent north pole thereof, flux will pass upwardly through a non-coil-carrying core 25 to a south pole of magnet m. Thus, at the moment illustrated'in Figs. 2 and 3, a magnetic circuit in one direction through each coil has just been broken and a m gnetic circuit in the opposite direction just established,thus securing a reversal of flux and therefore a larg flux change. At this moment, the cam separates the breaker points 46 and 41 and a spark is produced. There will be eight such breaks and flux reversals during each revolution of shaft II and the breaker point cam has eight projections to cause an opening of the primary circuit at each of said breaks.

It will be noted that the construction aifords a compact arrangement of parts. The coils are placed as closely as possible to the drive shaft and for a given size of coil the diameter of the casing is as small as it is feasible to make it in a high tension magneto, where both primary and secondary coils are used. The coils are packedso closely together that no room is available for coils on four of the cores. While these last mentioned four cores might also be. equipped with coils, if desired, this would mean an increase in diameter of the magneto casing, with the result that it might be too bulky for the timer-type mounting. The coils constitute the limiting factor here. No difllculty is presented in getting the magnets within the desired space limitations because they are made 0K special steel,

which by reason of high quality rather than large dimensions, produces all the flux that is needed. The magnets, though small, are of exceedingly high coercive force. The arrangement lends itself to the use of two magnets in series in each of the four magnetic circuits. Some means has to be provided for interconnecting adjacent cores at their lower ends and, while such means might merely be magnetizable material, it is advantageously made of permanently magnetic material because of the added supply of flux thereby secured.

The invention thus ailords an exceedingly compact arrangement of parts in a high tension magneto, with all moving parts kept to as low weight as feasible and the heavier parts,the coils and cores,1ocated stationarily between the two rotors andv packed closely around the shaft.

What I- claim is:

1. Amagneto, comprising, a driving shaft, a pair of rotors fixed thereto in axially spaced relation and each comprising a plurality of radially extending arms, a stator mounted between the arms of the two rotors and surrounding said shaft, said stator comprising a circular series of cores equal in number to the arms of a rotor, each core mounted in substantially parallel relation with said shaft and having its ends located in inductive relation one with the arms of one rotor and the other with the arms of the other rotor, at least one of said rotors being a permanent magnet with alternate arms of opposite polarity, and coil units mounted one unit on alternate cores of the series and each comprising a primary and a secondary coil.

2. A magneto, comprising, a driving shaft, a pair of rotors fixed thereto in axially spaced relation and each comprising a plurality of radially extending arms, a stator mounted between the arms of the two rotors and surrounding said shaft, said stator comprising a circular series of cores equal in number to the arms of a rotor,

each core mounted in substantially parallel rela- .magnet with alternate arms of opposite polarity,

each arm of one rotor being of opposite polarity to the corresponding and opposed arm of the other rotor, and coil units mounted one on alterprimary anda secondary coil.

KENNETH a much. 

